Oracle's Sun Java JDK packages are to be removed from the Ubuntu partner repositories and disabled on users systems. Oracle, in retiring the "Operating System Distributor License for Java," means Canonical no longer have permission to distribute the package. The change will affect Ubuntu 10.04 LTs, Ubuntu 10.10 and 11.04 users only. Users who have the "sun-java-6" package installed on their system will see it removed via a future software update -- the exact date of which is "TBD."

If Oracle says that JRE 1.7 is based in OpenJDK, then JRE 1.7 should not work with some legacy apps too.

That means they have broken the legacy, not that they removed Java license from Ubuntu to screw up consumers.

The question may be. How different are the binaries of OpenJDK against Oracle Java 7 JRE?

Actually, that is exactly what they did. I'm running Windows 7, and have Java 7 JRE installed. While it doesn't crash nearly as often as the OpenJDK on Linux, there are numerous Java applications (the sections of LibreOffice coded in Java come to mind) that are highly unstable on it.